Summary The pilot of the amateur-built Pitts S1S aerobatic biplane (registration C-FZSF, serial number 500607-97) was on a local flight from his private grass airstrip in Melancthon, Ontario, when the aircraft struck the ground following a low-level roll. The impact and post-crash fire destroyed the aircraft. The pilot, the only person on board, received fatal injuries. The accident happened at 1959eastern daylight time during twilight hours. Ce rapport est galement disponible en franais. Other Factual Information The pilot held a valid airline transport pilot licence. Since learning to fly in 1973, he had accumulated in excess of 22000hours flying in all areas of the world on numerous aircraft types, including the Douglas DC-3, the de Havilland DHC-7 and DHC-8, and the Gulfstream G2,G3, andG4. He was currently employed as chief pilot for a large company, and held current type ratings on 19different aircraft types. The pilot had received formal aerobatic training in a Zlin aircraft. Following this training, he purchased a Smith Miniplane, which he used for aerobatic practice. In October1999, he purchased the PittsS1S. This PittsS1S was an amateur-built, single-seat, aerobatic biplane, which had been built in Saskatoon, Saskatchewan, and first flown on 19April1997. When purchased, the aircraft had a total time of 137hours. Since that time, the pilot had flown approximately 160hours in the PittsS1S. The majority of the flights were for aerobatic practice, and lasted less than one hour. At the time of the accident, there were no outstanding maintenance snags and there was no history of repeating maintenance issues. Transport Canada had issued the pilot a letter of authorization for conducting aerobatic flight below 2000feet above ground level (agl). There are no competency requirements for this approval. On the evening of the occurrence, the pilot decided to fly a circuit before tying the aircraft down for the night. At the same time, the pilot of another aircraft, a PiperJ-3Cub, was preparing to fly back to his own airstrip. Each pilot was aware of the other. The Pitts pilot departed to the southwest at approximately 1955eastern daylight time.1 Shortly after the Pitts took off, the Cub pilot departed to the southwest, turned to the east, and climbed to 500feetagl. The Pitts pilot then caught up to the Cub and turned in front of it, in a steeply banked turn and at a slightly higher altitude. The Pitts completed two 360-degree turns around the Cub and then entered a roll. Almost immediately after the roll was completed, the Pitts struck the ground in a flat field. The pilots did not discuss this activity before taking off. The accident site was approximately one mile from the pilot's airstrip. On impact, the aircraft was travelling in an easterly direction in a wings-level, nose-low attitude. Although the exact pitch attitude could not be determined, the aircraft was pitched nose down such that the propeller was the first part of the aircraft to contact the ground. A post-mortem examination showed that the pilot died as a result of trauma sustained at impact and did not reveal any pre-existing medical conditions that would have contributed to the accident. There were no identifiable anomalies in the flight control system, aircraft structure, engine (Lycoming IO-360-B1D), or propeller that would have affected the pilot's ability to control the aircraft. All failures in the elevator control system and other aircraft parts and systems were determined to be impact-related, and there was no indication of anything jamming the controls. It was determined that the aircraft was flying at a speed between 120and 140mph when it struck the ground. Engine rpm at impact was2150. Weather conditions at the time were as follows: calm wind, visibility 15 statute miles, a broken to overcast cloud layer at approximately 1000feetagl, and the horizon to the west was clear. Sunset was at1946, and official night, by definition hour after sunset, was at2016. The human eye adapts to changing light conditions. However, it is slow to adapt from bright light to low-light conditions. From one extreme to the other can take an adaptation of up to 45minutes.2 Each time the eye is exposed to the bright light, the process of dark adaptation has to begin again.